The plan calls for retiring two older coal units at the Clay Boswell plant in Cohasset by 2022. That’s two years earlier than the Duluth-based utility proposed. The Taconite Harbor plant in Schroeder would stop burning coal permanently by 2020.

Minnesota Power plans to invest more in wind, solar and natural gas. But regulators called for more analysis on the right mix within the next few years.

Environmental groups are happy the commission made changes to the utility’s original plan in favor of clean energy, Sierra Club organizer Jessica Tritsch said.

“Fossil fuels we know are costly to our health, to our climate, to our well-being, and this really sets us on a path where Minnesota Power can really move forward with retiring old, dirty coal plants and look toward wind, solar and energy efficiency to meet new needs,” Tritsch said.

Environmental groups remain concerned about climate change and also argue that relying too much on fossil fuels could be more expensive for Minnesota utility customers in the long run.

Minnesota Power said its long-term goal is to transition from about 75 percent coal generation now to one-third coal, one-third renewables and one-third natural gas. Utility officials call the strategy EnergyForward. Minnesota Power generated about 95 percent of its electricity from coal 10 years ago.